Experimental evidence for strong emergent correlations between particles in a switching trap

TL;DR

This study experimentally demonstrates that collective switching in a system of trapped Brownian particles induces strong, long-range correlations that dominate over hydrodynamic interactions, with results aligning well with theoretical predictions.

Contribution

It provides the first experimental evidence of switching-induced emergent correlations in a many-particle system, surpassing hydrodynamic effects and confirming theoretical models.

Findings

Switching induces strong long-range correlations.

Correlations dominate over hydrodynamic interactions.

Experimental results agree with theoretical predictions.

Abstract

We experimentally study a gas of $N = 8$ one-dimensional Brownian particles, each confined in a harmonic trap with identical stiffness. The stiffness switches simultaneously between two values at random Poissonian times. This collective switching drives the system into a non-equilibrium stationary state (NESS) with strong long-range correlations between the positions of the particles. Remarkably, we find that these switching-induced emergent correlations completely overwhelm the hydrodynamic interactions between the particles mediated via the surrounding fluid. Comparing with exact theoretical predictions for noninteracting particles, we observe excellent agreement between theory and experiments for multiple observables, including the correlations between particles, extreme value and order statistics (maxima, minima and ranked positions) and the full counting statistics (i.e., the distribution of the number of particles in a finite interval $[-L, L]$ around the trap center).